Battery pack

Abstract

The purpose of the present invention is to prevent inducement of thermal runaway while reducing manufacturing costs.　In this battery pack, a plurality of battery cells that are are cylindrical in shape and that are capable of charging and discharging are stored in an exterior case in mutually parallel orientations, with a heat-resistant wall (3) being positioned between the battery cells. The heat-resistant wall (3) has a heat-insulated recess (4) that forms an air layer having a length (L) extending in the long-axis direction of the battery cells and a lateral width (W) extending in the circumferential direction, the heat-insulated recess (4) being located in a surface facing the surfaces of the battery cells.

Description

[Technical Field]

[0001] The present invention relates to a battery pack in which a plurality of battery cells are housed in an exterior case. [Background technology]

[0002] Battery packs, which contain multiple battery cells housed in an outer case, are used as power sources for electrical devices. These battery packs increase capacity by connecting multiple battery cells in series or parallel. In recent years, there has been a demand for higher capacity battery packs, while efforts have been made to increase the capacity of each individual battery cell. Furthermore, battery packs are increasingly being designed to place battery cells close together with no gaps between them.

[0003] On the other hand, it is extremely difficult to completely eliminate the possibility of thermal runaway in battery cells due to various causes, such as internal short circuits and overcharging. In a battery pack in which multiple battery cells are arranged closely together, if one of the battery cells generates abnormal heat and goes into thermal runaway, there is a risk of it emitting high-temperature exhaust gases with a large amount of thermal energy. If the exhaust gases emitted from a thermally runaway battery cell heat adjacent battery cells and induce thermal runaway, they will emit even more thermally energetic exhaust gases, which will reduce safety. To prevent this problem, a battery pack must be designed so that even if one battery cell goes into thermal runaway, this thermal runaway will not induce thermal runaway in adjacent battery cells.

[0004] To prevent the above problems, battery packs have been developed that place mica plates between adjacent battery cells (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-33464 [Patent Document 2] International Publication No. 2019 / 150772 Summary of the Invention [Problem to be solved by the invention]

[0006] The battery packs described in Patent Documents 1 and 2 have curved mica plates that are in close contact with the surfaces of cylindrical batteries and are arranged along the surfaces. The battery pack described in Patent Document 1 has curved mica plates arranged on the surfaces of adjacent cylindrical batteries, and a plastic heat-resistant wall is arranged between the mica plates to prevent thermal runaway. The battery pack described in Patent Document 2 has curved mica plates arranged on the surfaces of adjacent cylindrical batteries, and another flat mica plate is arranged between the opposing mica plates to prevent thermal runaway. These battery packs have two layers of mica plates between adjacent cylindrical batteries, and a plastic or mica heat-resistant wall is arranged between the two mica plates, which has the disadvantage of being complex in structure and high in manufacturing costs.

[0007] The present invention was developed with the aim of overcoming the above drawbacks, and one of the objects of the present invention is to provide a battery pack that can prevent the induction of thermal runaway while reducing manufacturing costs. [Means for solving the problem]

[0008] A battery pack according to one embodiment of the present invention houses a plurality of cylindrical, chargeable and dischargeable battery cells in a parallel orientation in an exterior case with a heat-resistant wall disposed between them. The heat-resistant wall has a heat-insulating recess on the surface facing the battery cell surface, which forms an air layer with a length (L) extending in the longitudinal direction of the battery cell and a width (W) extending in the circumferential direction. The heat-resistant wall is made of two heat-resistant plates stacked at the center where an insulating recess is provided, and the heat-resistant wall has inner grooves between both sides of the stacked heat-resistant plates, with the openings closed by the inner surface of the outer case on both sides of the center. [Effects of the Invention]

[0009] The battery pack according to the present invention has a heat-resistant wall between parallel-positioned battery cells, which has a heat-insulating recess that forms an air layer on the surface facing the battery cell, thereby suppressing heat conduction to adjacent battery cells and effectively preventing thermal runaway. In particular, the battery pack described above has a simple structure in which a heat-resistant wall is placed between parallel-positioned battery cells, and can effectively prevent thermal runaway while reducing manufacturing costs. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a battery pack according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional view of the battery pack shown in FIG. 1 taken along line II-II. [Figure 3] FIG. 2 is an exploded perspective view of the battery pack shown in FIG. [Figure 4] 2 is an exploded perspective view of the battery pack shown in FIG. 1, seen from the bottom. FIG. [Figure 5] FIG. 3 is an enlarged cross-sectional view of the battery pack shown in FIG. [Figure 6] FIG. 5 is a bottom view of the core pack of the battery shown in FIG. 4. [Figure 7] FIG. 10 is a schematic perspective view showing how exhaust flames from the side surfaces of the battery cells are discharged to the outside through the heat insulating recesses in the heat-resistant wall. [Figure 8] FIG. 10 is a schematic perspective view showing how exhaust flames from the side surfaces of the battery cells are discharged to the outside through the inner grooves of the heat-resistant wall. [Figure 9] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] A battery pack according to one embodiment of the present invention is a battery pack that comprises a plurality of cylindrical, chargeable and dischargeable battery cells that are parallel to one another and housed in an outer case with a heat-resistant wall disposed between them. The heat-resistant wall has an insulating recess on the surface facing the battery cell surface that forms an air layer with a length (L) extending in the longitudinal direction of the battery cell and a width (W) extending in the circumferential direction.

[0012] In a battery pack according to another embodiment of the present invention, the heat insulating recess has a length (L) that extends to both ends of the battery cell and is open at both ends of the battery cell.

[0013] The battery pack described above prevents thermal damage caused by exhaust gases by allowing the high-temperature exhaust gases discharged from the battery cells into the air space to flow from the battery cell surface to the outside through the insulating recesses. High-temperature exhaust gases stagnating in the air space between the battery cells and the heat-resistant wall can cause thermal damage to the heat-resistant wall, and damage to the heat-resistant wall can lead to thermal runaway.

[0014] In a battery pack according to another embodiment of the present invention, the heat insulating recess has a width (W) that includes the proximity portion where the outer circumferential surfaces of the battery cells are closest to each other.

[0015] In the battery pack described above, air layers can be provided on both sides of the adjacent portion of the outer peripheral surface of the cylindrical battery cell, so that exhaust gases ejected from the adjacent portion of the battery cell and from both sides thereof can flow into the air layers, preventing the induction of thermal runaway.

[0016] In a battery pack according to another embodiment of the present invention, the heat-resistant wall is made up of two heat-resistant plates stacked at the center where a heat insulating recess is provided.

[0017] The battery pack described above uses two heat-resistant plates stacked together to form the heat-resistant wall, which allows efficient mass production of heat-resistant walls with ideal cross-sectional shapes. This is because each heat-resistant plate can be formed into various shapes and stacked to create heat-resistant walls with complex cross-sectional shapes.

[0018] In a battery pack according to another embodiment of the present invention, the heat-resistant wall has outer grooves along both sides of the insulating recess, with openings disposed on the surfaces of the battery cells.

[0019] The battery pack described above has an insulating recess in the center of the heat-resistant wall with outer grooves on both sides, creating an air layer in the center of the heat-resistant wall due to the insulating recess and air layers in the outer grooves on both sides, creating three rows of air layers on the surface facing the battery cells. This structure, with three rows of air layers, creates a wide air layer on the cylindrically curved surface of the battery cells, allowing exhaust gases emitted from the battery cells to flow into the air layer over a wide area, preventing thermal runaway.

[0020] In a battery pack according to another embodiment of the present invention, the heat-resistant plate has bent pieces formed by bending both side edges toward the surfaces of the battery cells, and outer grooves are provided between the bent pieces and the surfaces of the battery cells.

[0021] In the above battery pack, two rows of outer grooves can be provided on the surface of the battery cells using folded pieces formed by bending both side edges of the heat-resistant plate, so that two rows of outer grooves can be provided on both sides of the insulating recess on the surface of the battery cells while maintaining a simple shape.

[0022] In another embodiment of the battery pack of the present invention, the heat-resistant wall has an inner groove between both side portions of the stacked heat-resistant plates, and between the outer grooves provided on both sides, the opening of which is blocked by the inner surface of the outer case.

[0023] In the battery pack described above, inner grooves are provided in the valleys formed by arranging cylindrically curved battery cells in a parallel position, and these inner grooves also function as air layers to provide thermal insulation between adjacent battery cells.

[0024] In a battery pack according to another embodiment of the present invention, the heat-resistant plate has first, second, and third bent portions extending in the longitudinal direction of the battery cells, and the first, second, and third bent portions are arranged in two rows from the center to both sides. The heat-resistant plate has a central flat portion between the first bent portions arranged in two rows in the center, raised portions extending from both side edges of the central flat portion toward the surfaces of the battery cells between the first and second bent portions, both side flat portions between the second and third bent portions, and folded pieces between the third bent portions and the side edges of the heat-resistant plate, where the central flat portion and the raised portions form a heat-insulating recess, the both side flat portions and the raised portions form inner grooves, and the both side flat portions and the folded pieces form outer grooves.

[0025] The above battery cells can be made into an ideal heat-resistant wall by bending and stacking two heat-resistant plates. In particular, the above battery pack is made by stacking two heat-resistant plates, with an insulating recess in the center of each side, outer grooves on both sides of the insulating recess, and an inner groove between the outer grooves on both sides of the heat-resistant wall, with the insulating recess, outer groove, and inner groove acting as an air layer to insulate adjacent battery cells. Therefore, by stacking two heat-resistant plates while giving the heat-resistant wall an ideal shape to prevent thermal runaway, it has the advantage of being able to reduce manufacturing costs and produce large quantities efficiently.

[0026] In a battery pack according to another embodiment of the present invention, the heat-resistant plate is an inorganic plate.

[0027] This battery pack has a heat-resistant wall with excellent heat resistance, and can effectively prevent thermal damage to the heat-resistant plate caused by exhaust gases emitted from the battery cells.

[0028] A battery pack according to another embodiment of the present invention is made of mica plates formed by bending inorganic plates, and the mica plates are joined in a stacked state at the center.

[0029] The battery pack described above uses mica plates made by bending heat-resistant boards, so the heat-resistant walls have excellent heat resistance characteristics. By bending and laminating the mica plates, the heat-resistant walls can be made into an ideal shape and can be mass-produced efficiently.

[0030] In another embodiment of the battery pack of the present invention, the heat-resistant wall is made of two mica plates that are bent at a first bend, a second bend, and a third bend, and the two mica plates are joined in a stacked state at their central flat portions.

[0031] In the battery pack described above, bent mica plates are stacked in the center to form a heat-resistant wall, so that in the area where the cylindrical battery cells are closest to each other, two mica plates with excellent heat resistance are stacked in two layers, achieving even better heat resistance. Furthermore, outer grooves are formed on both sides of the center with bent mica plates, so that the heat-resistant wall can have three rows of air layers on the opposing surfaces of adjacent battery cells, consisting of an air layer created by the insulating recesses, which have particularly excellent heat resistance, and an air layer created by the outer grooves. The three rows of air layers are arranged over a wide area on the opposing surfaces of the battery cells, effectively guiding exhaust gases emitted from the battery cells into the air layers, more effectively preventing thermal runaway.

[0032] In a battery pack according to another embodiment of the present invention, the width (W) of the heat insulating recess is 15% or more of the outer diameter of the battery cell.

[0033] In a battery pack according to another embodiment of the present invention, the width (W) of the heat insulating recess is 60% or less of the outer diameter of the battery cell.

[0034] In a battery pack according to another embodiment of the present invention, the minimum gap (d) between the heat-resistant wall and the surface of the battery cell in the heat-insulating recess is 5 mm or less.

[0035] A battery pack according to another embodiment of the present invention includes a temperature sensor for detecting the temperature of the battery cell, and the temperature sensor is disposed between the heat-resistant wall and the surface of the battery cell.

[0036] The above battery pack has a feature that the temperature sensor is arranged in thermal connection with the surface of the battery cell, and can quickly detect the temperature of the battery cell with high accuracy.

[0037] A battery pack according to another embodiment of the present invention includes a temperature sensor for detecting the temperature of the battery cell, and the temperature sensor is disposed in the outer groove.

[0038] The battery pack described above has the temperature sensor placed in an outer groove provided in the heat-resistant wall, which allows the temperature sensor to be easily placed in an ideal position while still being able to detect the temperature of the battery cells with greater accuracy.

[0039] A battery pack according to another embodiment of the present invention includes a voltage detection line connected to an end surface electrode of a battery cell to detect the voltage of the battery cell, and the voltage detection line is disposed in the outer groove.

[0040] The above battery pack has the voltage detection lines arranged in outer grooves in the heat-resistant wall, which has the advantage that the voltage of the battery cells can be detected while the voltage detection lines are arranged in fixed positions in a space-saving manner.

[0041] In another embodiment of the battery pack of the present invention, the outer case has a surface plate portion that is arranged in the same plane as the surfaces of multiple battery cells arranged in a parallel position, and the surface plate portion has a positioning rib that protrudes toward the inner surface, and the positioning rib is guided into the inner groove to position the heat-resistant wall in a fixed position on the outer case.

[0042] The battery pack described above has the advantage that the heat-resistant wall can be positioned in a fixed position on the outer case by guiding the positioning ribs on the surface plate of the outer case into the inner grooves of the heat-resistant wall.

[0043] Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concept of the present invention, and the present invention is not limited to these. Furthermore, this specification in no way specifies the components set forth in the claims as components of the embodiments. The dimensions, materials, shapes, and relative positions of components described in the embodiments are not intended to limit the scope of the present invention, and are merely illustrative unless otherwise specified. The size and relative positions of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate identical or similar components, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present invention may be configured with the same components, so that one component serves multiple functions, or conversely, the function of one component may be shared by multiple components. Furthermore, the content described in some examples and embodiments may be applicable to other examples and embodiments.

[0044] (Embodiment 1) A battery pack according to one embodiment of the present invention is shown in Figures 1 to 6. Figure 1 is a perspective view of a battery pack 100, Figure 2 is a cross-sectional view of the battery pack 100 of Figure 1 taken along line II-II, Figure 3 is an exploded perspective view of the battery pack 100 of Figure 1, Figure 4 is an exploded perspective view of the battery pack 100 of Figure 1 as seen from the bottom, Figure 5 is an enlarged cross-sectional view of the battery pack 100 of Figure 2, and Figure 6 is a bottom view of a battery core pack 10 in which a battery block 9 and a circuit board are connected.

[0045] The battery pack 100 contains multiple battery cells 1 that can be charged and discharged, and these cells are connected in series or parallel to increase capacity and enable charging and discharging. This battery pack 100 is connected to an external device to be driven, and power is supplied by discharging the battery cells 1. Here, an example is shown in which the external device to which the battery pack 100 is connected is a notebook computer. However, the external device to which the battery pack of the present invention can be connected is not limited to notebook computers, and other electronic or electrical devices, such as mobile phones, portable DVD players, portable car navigation systems, portable music players, power tools, and assisted bicycles, can also be connected. The battery pack can be directly and detachably attached to the external device, or it can be stored or embedded in the external device, or connected via a cable or the like.

[0046] The battery pack 100 shown in Figures 1 to 5 includes multiple cylindrical battery cells 1 that can be charged and discharged, an exterior case 2 that houses the multiple battery cells 1, and heat-resistant walls 3 that are placed between adjacent battery cells 1. In this battery pack 100, the multiple battery cells 1 are housed in the exterior case 2 in a parallel orientation with the heat-resistant walls 3 placed between them. The heat-resistant walls 3 have insulating recesses 4 on the surface facing the surface of the battery cells 1 that form an air layer with a length (L) extending in the longitudinal direction of the battery cells 1 and a width (W) extending in the circumferential direction. The battery pack 100 is structured so that the heat-resistant walls 3 placed between the battery cells 1 prevent thermal runaway from occurring in adjacent battery cells 1.

[0047] (Outer case 2) As shown in Fig. 1, the battery pack 100 is formed in a box shape that is approximately rectangular in plan view. The box-shaped main body is made up of an exterior case 2. As shown in Figs. 3 and 4, the exterior case 2 is divided into a lower case 2A and an upper case 2B. The exterior case 2 is provided with a connector 14 for connecting to an electrical device (here, a notebook computer) to be driven by the battery pack 100. The exterior case 2 may also be provided with a connection mechanism for connecting the battery pack 100 to the electrical device and a locking mechanism for maintaining the battery pack 100 in an attached state. The exterior case 2 is made of a material with excellent insulating and heat-insulating properties, for example, a resin such as polycarbonate.

[0048] As shown in Figures 2 to 5, the exterior case 2 contains multiple battery cells 1, heat-resistant walls 3 arranged between the battery cells 1, and a circuit board 8. The battery pack 100 shown in the figures is constructed by connecting lead plates 11 to the end surface electrodes on both ends of the battery cells 1 in a parallel orientation with heat-resistant walls 3 arranged between them, forming a battery block 9, and connecting the lead plates 11 of the battery block 9 to the circuit board 8, which is then housed in the exterior case 2 as a battery core pack 10 with the circuit board 8 connected.

[0049] (Battery cell 1) Battery cell 1 is a lithium-ion secondary battery. However, battery cell 1 can also be a non-aqueous electrolyte secondary battery other than a lithium-ion secondary battery, and battery cell 1 can also be a rechargeable secondary battery such as a nickel-metal hydride battery or a nickel-cadmium battery, especially a battery that generates heat to a high temperature during use. Battery cell 1 uses a cylindrical battery with a cylindrical outer can.

[0050] As shown in Figure 6, multiple battery cells 1 are arranged parallel to one another to form a battery block 9. The battery block 9 in the figure has six cylindrical battery cells 1 arranged in six rows. In this battery block 9, two battery cells 1 are arranged in the same direction and their end faces are connected with lead plates 11 to form a parallel connection to form a battery group 1X, and three battery groups 1X are arranged alternately in opposite directions and their end faces are connected with lead plates 11 to connect adjacent battery groups 1X in series, resulting in a two-in-one parallel / three-in-series connection of the six battery cells 1. Although the battery block 9 in the figure has six battery cells 1 connected in two in parallel / three in series, the number of battery cells 1 and the connection configuration can be freely changed.

[0051] The multiple battery cells 1 are electrically connected in series or parallel via lead plates 11. The lead plates 11 are made by bending highly conductive metal plates. The lead plates 11 are welded to the end electrodes of the battery cells 1. The positive and negative outputs of the battery block 9 are connected to the circuit board 8 via output leads 11a and 11b. The circuit board 8 is equipped with charge / discharge circuits and protection circuits. To monitor the voltage of each battery cell 1, the circuit board 8 connects connection leads 11c and 11d on the lead plates 11 for measuring the intermediate potential directly or via a voltage detection line 12. It also connects a temperature sensor 13 to detect the temperature of each battery cell 1. A thermistor or similar device is used as the temperature sensor 13. The circuit board 8 shown in the figure has a connector 14 directly connected to it, which is exposed to the outside through an opening 2b in the exterior case 2 so that it can be connected to external devices.

[0052] (Heat-resistant wall 3) The heat-resistant walls 3 are placed between the battery cells 1 to suppress heat conduction between adjacent battery cells 1 and to prevent exhaust gases ejected from the side of a battery cell 1 that has experienced thermal runaway from adversely affecting the adjacent battery cells 1. In a cylindrical battery cell 1, when thermal runaway occurs, exhaust gases may not only be ejected from a gas valve on the end face, but may also be ejected by the battery cell 1 splitting open from its side. In a battery pack with a structure in which multiple battery cells 1 are arranged parallel to one another, it is important to prevent thermal runaway from being triggered by exhaust gases ejected when the side of a battery cell 1 splits open during thermal runaway. In the battery pack of the present invention, these adverse effects are eliminated by placing a uniquely shaped heat-resistant wall 3 between adjacent battery cells 1.

[0053] The heat-resistant wall 3 is made of a material with excellent insulating and heat-resistant properties. It is preferably made of an inorganic material, such as mica. Mica is highly flame-retardant and non-flammable, has excellent insulating properties, and is relatively inexpensive, making it suitable for components requiring heat resistance and insulation. The heat-resistant wall 3, with its excellent heat resistance, does not burn or melt even when exposed to high-temperature exhaust gases and flames emitted from the battery cells 1, and can prevent the exhaust gases and flames from passing through the heat-resistant wall and reaching adjacent battery cells 1. Furthermore, to suppress heat conduction to adjacent battery cells 1, the heat-resistant wall 3 has insulating recesses 4 on both sides of the center of the wall that face the battery cell 1 surface. These recesses 4 form an air layer with a length (L) extending in the longitudinal direction of the battery cell 1 and a width (W) extending in the circumferential direction. The heat-resistant wall 3, located between the battery cells 1, forms two air layers between the adjacent battery cells 1 with the insulating recesses 4, thereby suppressing heat conduction between the adjacent battery cells 1.

[0054] Furthermore, the insulating recess 4 also functions as an exhaust path to direct high-temperature exhaust gases and flames ejected from the cracks in the side of the battery cell 1 in a specific direction. If a battery cell 1 malfunction causes a flame to escape, the direction of the flame is difficult to predict. If the flame reaches other battery cells 1, there is a risk of the flame spreading and causing thermal runaway. Therefore, by intentionally providing an exhaust path, even if a flame escapes, it is possible to suppress unintended runaway of the battery cell 1 and control the flow of the flame. In other words, by providing an exhaust path within the battery pack 100 using the heat-resistant wall 3, it is possible to configure the flame to flow in a specific direction, even if a flame escapes. The insulating recess 4 shown in Figure 7 has a length (L) that extends to both ends of the battery cell 1 and is open at both ends of the battery cell 1. In this way, by making the insulating recess 4 long enough to extend to both ends of the battery cell 1 (L) and leaving both ends open, the high-temperature exhaust gas and flames that are discharged from the side of the battery cell 1 into the air space in the insulating recess 4 as shown by arrow A in Figure 5 can be caused to flow out from the surface of the battery cell 1 to the outside via the insulating recess 4 as shown by the arrow in Figure 7, thereby controlling the flow of the exhaust gas and flames and effectively preventing the induction of thermal runaway.

[0055] The width (W) of the insulating recess 4 shown in Figure 5 is specified so as to include the close-up portion 1a where the outer peripheral surfaces of a pair of battery cells 1 are closest to each other in a cross-sectional view. When placed between adjacent battery cells 1, this heat-resistant wall 3 reliably guides the close-up portion 1a, where the outer peripheral surfaces are closest, into the insulating recess 4, preventing heat conduction between adjacent battery cells 1 over the shortest distance. Furthermore, by setting the width (W) of the insulating recess 4 to include the close-up portion 1a of the battery cells 1, air layers can be created on both sides of the close-up portion 1a. In the event of a rupture at the close-up portion 1a of the battery cells 1 or on either side of it, the emitted exhaust gases and flames can be reliably directed into the insulating recess 4, restricting their direction of emission.

[0056] The width (W) of the insulating recess 4 can be set to 15% or more, preferably 20% or more, and more preferably 25% or more of the outer diameter (D) of the battery cell 1. The width (W) of the insulating recess 4 can be set to 60% or less, preferably 50% or less, and more preferably 40% or less of the outer diameter (D) of the battery cell 1.

[0057] (Heat-resistant plate 30) As shown in Figure 9, the heat-resistant wall 3 in Figure 5 is formed by stacking two heat-resistant plates 30. The two heat-resistant plates 30 are joined together in the center and have insulating recesses 4 on both sides. The heat-resistant plates 30 are plates that do not deform due to the temperature of abnormally heated battery cells 1, and are preferably made of inorganic material such as mica plates. Instead of mica plates, inorganic powders sintered or molded into plates, or plate-shaped inorganic materials or inorganic fibers molded into plates can also be used as inorganic plates.

[0058] As shown in FIG. 5 , the heat-resistant wall 3 formed from two heat-resistant plates 30 has outer grooves 5 that are located on the surface of the battery cells 1 along both sides of the insulating recess 4. The heat-resistant plate 30 shown in the figure has both side edges bent toward the surface of the battery cells 1 to form folded pieces 37, and the outer grooves 5 are formed between these folded pieces 37 and the surface of the battery cells 1. By forming the folded pieces 37 by bending both side edges of the heat-resistant plate 30, this heat-resistant wall 3 can have two rows of outer grooves 5 on the surface of the battery cells 1 on both sides of the insulating recess 4. This heat-resistant wall 3 has an insulating recess 4 in the center and outer grooves 5 on both sides. Therefore, an air layer is created by the insulating recess 4 in the center of the heat-resistant wall 3, and air layers are created by the outer grooves 5 on both sides, creating three rows of air layers on the surface facing the battery cells 1. This structure uses three rows of air layers to create a wide air layer on the cylindrically curved surface of the battery cell 1, allowing the high-temperature exhaust gas and flames emitted from the battery cell 1 to flow into the air layer over a wide area, preventing the induction of thermal runaway.

[0059] Furthermore, by providing bent pieces 37 on both side edges of the heat-resistant plate 30, the heat-resistant wall 3 can have both the upper and lower ends of the heat-resistant wall 3 approach or come into contact with the inner surface of the exterior case 2 over a wide area, as shown in Figure 5. This structure increases the creepage distance of high-temperature exhaust gas and flames emitted from a thermally runaway battery cell 1 as they flow toward adjacent battery cells 1. This effectively prevents the high-temperature exhaust gas and flames emitted from the battery cell 1 from passing between the heat-resistant wall 3 and the exterior case 2 and reaching adjacent battery cells 1.

[0060] Furthermore, as shown in Figures 5 and 6, the heat-resistant wall 3 utilizes the outer groove 5 as a storage space for the temperature sensor 13. This structure effectively prevents the temperature sensor 13 placed in the outer groove 5 from floating up and separating from the surface of the battery cell 1. As a result, the temperature sensor 13 can be guided into the outer groove 5 from the tip side of the bent piece 37, and can be easily placed in a fixed position while accurately detecting temperature, without having to thermally attach the temperature sensor to the battery cell surface using a thermally conductive adhesive or the like, as in the past. The temperature sensor 13 guided into the outer groove 5 is held in place by attaching fixing tape 15 across adjacent battery cells 1 in the area where the temperature sensor 13 is stored, as shown by the dashed lines in Figures 5 and 6. Furthermore, the outer groove 5 of the heat-resistant wall 3 can also be used as a storage space for the voltage detection line 12, as shown in Figure 6. Here, the creepage distance of the heat-resistant wall 3 can be increased by lengthening the bending pieces 37, but if the bending pieces 37 are too long, bending the heat-resistant plate 30 becomes difficult and the gap between the tip of the bending piece 37 and the surface of the battery cell 1 becomes narrow, making it difficult to smoothly insert the temperature sensor 13, voltage detection line 12, etc. Therefore, taking these factors into consideration, the length of the bending pieces 37 of the heat-resistant wall 3 is specified so that a gap of 1 mm or more, and preferably 2 mm or more, is formed between the tip edge of the bending piece 37 and the surface of the battery cell 1.

[0061] Furthermore, the heat-resistant wall 3 has inner grooves 6 between both side portions of the stacked heat-resistant plates 30 and between the outer grooves 5 on both sides. The heat-resistant wall 3 shown in Figure 5 has inner grooves 6 in the valleys formed by arranging cylindrically curved battery cells 1 in a parallel position. As shown in Figure 2, when the battery core pack 10 is housed in the outer case 2, the openings of these inner grooves 6 are closed by the inner surface of the outer case 2, and the spaces between the inner grooves 6 and the outer case 2 serve as air layers, providing thermal insulation between adjacent battery cells 1. In particular, by providing three rows of air layers in the valley regions between adjacent battery cells 1, consisting of the air layers formed by the outer grooves 5 on the surface of each battery cell 1 and the air layers formed by the inner grooves 6 between the left and right outer grooves 5, an excellent thermal insulation structure can be achieved.

[0062] Furthermore, this inner groove 6 also functions as an exhaust path for directing high-temperature exhaust gases and flames ejected from cracks in the side surface of the battery cell 1 in a specific direction. When a crack occurs in the side surface of the battery cell 1 and high-temperature exhaust gases and flames are ejected as shown by arrows A and B in Fig. 5, the inner groove 6 positioned in this position allows the high-temperature exhaust gases and flames to flow toward the adjacent battery cell 1 as shown by arrow C in Fig. 5. Even if they pass through the front bent piece 37, they will not pass through the opposite bent piece 37 and will instead be discharged to the outside using this inner groove 6 as an exhaust path as shown by the arrow in Fig. 8. In other words, the exhaust gases and flames that are ejected from the side surface of the battery cell 1 and pass through the front bent piece 37 are directed in a specific direction via the inner groove 6, thereby controlling the flow of the exhaust gases and flames and effectively preventing thermal runaway from occurring in the adjacent battery cell 1.

[0063] As shown in FIGS. 5 and 9 , the heat-resistant wall 3 is formed into a predetermined cross-sectional shape by bending an inorganic heat-resistant plate 30 into a predetermined shape and then stacking and joining two heat-resistant plates 30 at their centers. The structure of forming the heat-resistant wall 3 by stacking two heat-resistant plates 30 allows efficient mass production of heat-resistant walls 3 with complex cross-sectional shapes, in which each heat-resistant plate 30 is shaped into various shapes to achieve an ideal shape. In particular, stacking and joining heat-resistant plates 30 of the same shape together allows efficient mass production of heat-resistant walls 3 with vertically and horizontally symmetrical cross-sectional shapes, reducing manufacturing costs. Here, depending on the type of inorganic board, the inorganic material may be heated and compressed in a mold or the like together with a resin, binder, etc. to form the predetermined shape. In this specification, such forming is also considered to be included in the bending process.

[0064] 5 and 9, each heat-resistant plate 30 constituting the heat-resistant wall 3 has a first bent portion 31, a second bent portion 32, and a third bent portion 33 that extend in the longitudinal direction of the battery cell 1. The first bent portions 31, the second bent portions 32, and the third bent portions 33 are arranged in two rows from the center toward both sides. Furthermore, the heat-resistant plate 30 has a central flat portion 34 between the first bent portions 31 arranged in two rows in the center, raised portions 35 formed between the first bent portions 31 and the second bent portions 32 that extend from both side edges of the central flat portion 34 toward the surface of the battery cell 1, both side flat portions 36 formed between the second bent portion 32 and the third bent portion 33, and bent pieces 37 formed between the third bent portion 33 and the side edges of the heat-resistant plate 30. The heat-resistant plate 30 shown in the figure has a central flat portion 34 and rising portions 35 on both sides that form an insulating recess 4, both side flat portions 36 and rising portions 35 that form an inner groove 6, and both side flat portions 36 and bent pieces 37 that form an outer groove 5.

[0065] The insulating recess 4, formed by the central flat surface 34 and the raised portions 35 on both sides, forms an air layer between the central flat surface 34 and the battery cell 1. The width (W) and depth of the insulating recess 4 are determined so that an air layer is formed between the surface of the battery cell 1 placed therein and the central flat surface 34. The insulating recess 4 is formed so that the minimum gap (d) between the surface of the battery cell 1 and the central flat surface 34 is 5 mm or less. Furthermore, the insulating recess 4 is preferably formed so that a gap is created between the close portion of the battery cell 1 surface and the central flat surface 34. The width (W) and depth of the insulating recess 4 are determined so that a minimum gap (d) of 0.5 mm or more, preferably 1 mm or more, is formed between the close portion of the battery cell 1 surface and the central flat surface 34. The opening of the insulating recess 4 is closed by the surface of the battery cell 1 placed therein. The heat-resistant plate 30 shown in Fig. 5 is chamfered on the battery cell 1 side of the second bent portion 32 so that a wide area can come into contact with the surface of the battery cell 1, and the contact portion with the battery cell 1 is made into an inclined surface. Also, the first bent portion 31 shown in Fig. 5 is formed by bending the heat-resistant plate 30 at an obtuse angle on both ends of the central flat portion 34 to provide raised portions 35. However, the first bent portion can also bend the heat-resistant plate 30 at a right angle or an acute angle.

[0066] The heat-resistant wall 3 shown in FIG. 9 is made up of two mica plates 30A bent at a first bent portion 31, a second bent portion 32, and a third bent portion 33. The two mica plates 30A are joined in a stacked state at a central flat portion 34. The two mica plates 30A joined at the central flat portion 34 have heat-insulating recesses 4 formed on both sides. In the central region where the cylindrical battery cells 1 are closest, two mica plates 30A with excellent heat resistance are stacked in two layers, achieving even better heat resistance. The two mica plates 30A are joined at their opposing central flat portions 34 using an adhesive. For example, an epoxy adhesive can be used as such an adhesive.

[0067] (Circuit board 8) The circuit board 8 is bent in an L-shape in plan view and is arranged along two sides of the rectangular battery block 9 in plan view, as well as along two sides of the peripheral wall of the box-shaped outer case 2. The L-shaped circuit board 8 has a first region 8A and a second region 8B that are connected at a right angle. The first region 8A is on one side of the battery block 9 and is arranged along the side of the cylindrical battery cells 1. The second region 8B is on one end face of the battery block 9 and is arranged opposite one end face of the cylindrical battery cells 1. The illustrated circuit board 8 has an external connection connector 14 fixed to the first region 8A, and the second region 8B is connected to a connection lead 11c for detecting the voltage of each battery group 1X, a voltage detection line 12 connected to a connection lead 11d, and a temperature sensor 13 for detecting the temperature of each battery cell 1. Furthermore, one output lead portion 11a of the lead plate 11 connected to the battery block 9 is connected to one end of the first region 8A of the L-shaped circuit board 8, and the other output lead portion 11b of the lead plate 11 connected to the battery block 9 is connected to one end of the second region 8B of the L-shaped circuit board 8.

[0068] (positioning rib) Furthermore, the exterior case 2 shown in FIGS. 2 to 5 includes a surface plate portion 2a that is flush with the surfaces of the multiple battery cells 1 arranged in parallel. The inner surface of the surface plate portion 2a is provided with a positioning rib 16 for positioning the heat-resistant wall 3 of the battery core pack 10 housed in the exterior case 2 in a fixed position. The positioning ribs 16 shown in FIGS. 3 and 4 are a pair of parallel ribs 16A formed parallel to each other. The pair of parallel ribs 16A are spaced apart to allow them to be guided into the inner groove 6. By inserting the pair of parallel ribs 16A into the inner groove 6, the heat-resistant wall 3 can be positioned and placed in a fixed position on the inner surface of the exterior case 2. For example, by adjusting the spacing of the pair of parallel ribs 16A so that they are press-fitted along the inner surface of the inner groove 6, the heat-resistant wall 3 can be fixed in place relative to the exterior case 2 with the pair of parallel ribs 16A inserted into the inner groove 6. However, the pair of parallel ribs 16A may also be spaced apart to allow smooth insertion into the inner surface of the inner groove 6.

[0069] As shown in Figure 4, the positioning rib 16 formed on the inner surface of the upper case 2B has a total length roughly equal to that of the heat-resistant wall 3, and is designed to fit over almost the entire inner groove 6 formed in the upper part of the heat-resistant wall 3. This structure, in which the heat-resistant wall 3 is connected via the positioning rib 16 that is inserted over almost the entire inner groove 6, reliably prevents high-temperature exhaust gases and flames emitted from the battery cells 1 from passing between the heat-resistant wall 3 and the outer case 2. Furthermore, as shown in Figure 3, the positioning rib 16 formed on the inner surface of the lower case 2A has a total length that connects it to a portion of the heat-resistant wall 3. In this way, the positioning rib 16 that is partially connected to the heat-resistant wall 3 is located in a position that does not affect the fixing tape 15 attached to the surface of the battery cell 1. [Industrial Applicability]

[0070] The battery pack according to the present invention can be suitably used as a rechargeable battery pack for battery-powered devices such as notebook computers, mobile phones, portable DVD players, portable car navigation systems, portable music players, power tools, and assisted bicycles. [Explanation of symbols]

[0071] 100...Battery pack 1...Battery cell 1a...Approach section 1X…Battery set 2...Outer case 2A...Lower case 2B...Upper case 2a...Surface plate part 2b...Opening window 3…Heat-resistant wall 4...Insulating recess 5...Outer groove 6...Inner groove 8...Circuit board 8A…First area 8B…Second area 9...Battery block 10...Core Pack 11...Reed plate 11a, 11b...Output lead section 11c, 11d...Connection lead part 12...Voltage detection line 13...Temperature sensor 14...Connector 15...Fixing tape 16... Positioning rib 16A...Parallel ribs 30...Heat-resistant plate 30A...mica plate 31...First bend 32...Second bend 33...Third bend 34...Central plane part 35...Rising part 36...Both flat surfaces 37...Bent piece

Claims

1. A battery pack is a battery pack that contains a plurality of cylindrical chargeable and dischargeable battery cells in parallel positions, with heat-resistant walls disposed between the cells, and is housed in an exterior case. the heat-resistant wall has a heat-insulating recess on a surface facing the battery cell surface, the heat-insulating recess forming an air layer having a length (L) extending in the longitudinal direction of the battery cell and a width (W) extending in the circumferential direction of the battery cell; The heat-resistant wall is made of two heat-resistant plates stacked at a central portion where the heat-insulating recess is provided, The heat-resistant wall is located between both sides of the stacked heat-resistant plates, and has inner grooves on both sides of the central portion, the openings of which are closed by the inner surface of the exterior case.

2. A battery pack comprising a plurality of cylindrical, chargeable and dischargeable battery cells arranged parallel to one another and housed in an outer case with heat-resistant walls disposed between them, the heat-resistant wall has a heat-insulating recess on a surface facing the battery cell surface, the heat-insulating recess forming an air layer having a length (L) extending in the longitudinal direction of the battery cell and a width (W) extending in the circumferential direction of the battery cell; the heat insulating recess has a width (W) including a proximity portion where the outer peripheral surfaces of the adjacent battery cells are closest to each other, the adjacent cylindrical battery cells have their proximity portions disposed midway between valleys formed on both sides between the adjacent cylindrical battery cells, a gap is formed between the heat-resistant wall and the adjacent battery cell surfaces at their close portions, The heat insulating recess forms a discharge path for allowing ejected material ejected from the cleavage in the side surface of the battery cell to flow, and the discharge path extends in the longitudinal direction of the battery cell.

3. 3. The battery pack according to claim 1, The battery pack has a length (L) where the heat insulating recess extends to both ends of the battery cell and is open at both ends of the battery cell.

4. The battery pack according to any one of claims 1 to 3, The heat insulating recess has a width (W) that includes an area where the outer peripheral surfaces of the battery cells are closest to each other.

5. 5. The battery pack according to claim 1, The heat-resistant wall has outer grooves along both sides of the insulating recess, the outer grooves having openings disposed on the surfaces of the battery cells.

6. 6. The battery pack according to claim 5, The heat-resistant wall is made of two heat-resistant plates stacked at a central portion where the heat-insulating recess is provided, The heat-resistant plate has bent pieces formed by bending both side edges toward the surfaces of the battery cells, and the outer groove is provided between the bent pieces and the surfaces of the battery cells.

7. 7. The battery pack according to claim 5 or 6, The heat-resistant wall is made of two heat-resistant plates stacked at a central portion where the heat-insulating recess is provided, The battery pack has an inner groove provided between both side portions of the stacked heat-resistant plates and between the outer grooves provided on both sides.

8. The battery pack according to claim 7, the heat-resistant wall has bent pieces formed by bending both side edges toward the surface of the battery cell; the heat-resistant wall has a first bent portion, a second bent portion, and a third bent portion extending in the longitudinal direction of the battery cell; the first bent portion, the second bent portion, and the third bent portion are each arranged in two rows from a central portion toward both sides, The heat-resistant plate is a central plane portion is defined between the first bent portions arranged in two rows in the central portion, between the first bent portion and the second bent portion, rising portions are formed that extend from both side edges of the central flat portion toward surfaces of the battery cells, a pair of flat surfaces are formed between the second bent portion and the third bent portion, The bent piece is formed between the third bent portion and the side edge of the heat-resistant plate, the central flat portion and the rising portion form the heat insulating recessed portion, the inner groove is formed by the both side flat portions and the rising portions, The battery pack has the outer groove formed by the flat portions on both sides and the bent pieces.

9. 9. The battery pack according to claim 4, The heat-resistant wall is made of two heat-resistant plates stacked at a central portion where the heat-insulating recess is provided, The battery pack, wherein the heat-resistant plate is an inorganic plate.

10. 10. The battery pack of claim 9, The inorganic plate is a mica plate formed by bending, and the battery pack is formed by joining the mica plates in a stacked state at the center.

11. 9. The battery pack according to claim 8, the heat-resistant wall is made of two mica plates bent at the first bent portion, the second bent portion, and the third bent portion; The battery pack is formed by joining the mica plates in a stacked state at the central flat portion.

12. The battery pack according to any one of claims 1 to 11, A battery pack in which the width (W) of the heat insulating recess is 15% or more of the outer diameter of the battery cell.

13. 13. The battery pack according to claim 1, A battery pack in which the width (W) of the heat insulating recess is 60% or less of the outer diameter of the battery cell.

14. The battery pack according to any one of claims 1 to 13, The battery pack, wherein the minimum gap (d) between the heat-resistant wall and the surface of the battery cell in the heat-insulating recess is 5 mm or less.

15. 15. The battery pack according to claim 1, a temperature sensor for detecting the temperature of the battery cell; The battery pack has the temperature sensor disposed between the heat-resistant wall and the surface of the battery cell.

16. 12. The battery pack according to claim 5, wherein: a temperature sensor for detecting the temperature of the battery cell; The battery pack, wherein the temperature sensor is disposed in the outer groove.

17. 12. The battery pack according to claim 5, wherein: a voltage detection line connected to an end surface electrode of the battery cell to detect a voltage of the battery cell; The voltage detection line is disposed in the outer groove.

18. The battery pack according to any one of claims 7, 8 and 11, the exterior case includes a surface plate portion that is disposed flush with surfaces of the plurality of battery cells that are disposed in parallel, The surface plate portion has a positioning rib protruding toward the inner surface, and the positioning rib is guided into the inner groove to position the heat-resistant wall at a fixed position on the exterior case.

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